The sun is nearly down in San Francisco and Zak Zimmerman and David Puerta are worried about arriving late for their final meeting on a long day. It is the first day of the JPMorgan Healthcare Conference, and the men, leaders of the biotech start-up Forge Therapeutics, have been up since long before dawn. They walk briskly out of the Hotel Nikko and turn left on Powell Street toward Union Square, where swaths of men and the occasional woman are spilling out of nearby hotels to hit the first cocktail parties of the night. Zimmerman and Puerta weave through the crowds, cut across to Stockton Street, and start up the hill to the Ritz-Carlton.
